Is solving the health insurance problem to single founders / freelancers much more difficult than 2 founders? or is it much smaller market? Honest question, because as far as I understand both Zenefits and SimplyInsured (both YC13 and pretty similar market) do not address the |company| < 2 market.
First, they could always ask your ISP to route a copy of each smtp to their servers.
But this is a bit irrelevant until you solve the social problem: I'm going to guess that >90% of your contacts use gmail/yahoo/hotmail; so the NSA already has 90% of your mail in their databases anyways- until you convince your contacts to install their own email server.
> or they are participating voluntarily and are voluntarily lying, ... seems unlikely to me.
Their business is based on user's data. If you do not feel comfortable giving them your data, it might hurt their business. Hence, IMHO, they do have some incentive to deny PRISM, regardless of the facts.
[1] http://www.sec.gov/Archives/edgar/data/1579091/0001579091140...
[2] http://techcrunch.com/2014/12/05/instacart-2b-kleiner/
[3] http://bits.blogs.nytimes.com/2015/01/12/instacart-a-grocery...
[4] http://graphics.wsj.com/billion-dollar-club/